1. Field of the Invention
The present invention relates to a method for implementation in a semiconductor processing system, and more particularly, a method for increasing the service interval of a gas distribution plate and the like.
2. Description of the Prior Art
Ultra-large-scale integrated (ULSI) circuits may include more than one million electronic devices (e.g., transistors) that are formed on a semiconductor substrate, such as a silicon substrate, and cooperate to perform various functions within the device. Typically, the transistors used in the ULSI circuits are complementary metal-oxide-semiconductor (CMOS) field effect transistors. A CMOS transistor has a gate structure including a polysilicon gate electrode and gate dielectric, and is disposed between a source region and drain regions that are formed in the substrate. Such formation of integrated circuits involves sequentially forming or depositing multiple electrically conductive and insulative layers in or on the substrate. Etching processes may be used to form geometric patterns in the layers or vias for electrical contact between the layers. General etching processes include wet etching, in which one or more chemical reagents are brought into direct contact with the substrate, and dry etching, such as plasma etching.
Various types of plasma etching processes are known in the art, including plasma etching, reactive ion etching and reactive ion beam etching. In many of these plasma processes, a gas is first introduced into a reaction chamber through a gas distribution plate (GDP) and then plasma is generated from the gas. The ions, free radicals and electrons in the plasma react chemically with the layer material on the semiconductor substrate to form residual products which leave the substrate surface and thus, etch the material from the substrate. The gas distributed by the gas distribution plate not only provides the source for the ions, but can also be used to influence the lateral etch rate.
Before the etching process is performed, the substrate is coated with a layer of resist (for example, a photoresist), the resist is patterned, and the pattern is transferred to underlying layers by etching—with the patterned resist layer serving as an etch mask. Many such etching processes leave resist and post-etch residues on the substrate or substrate that must be removed or stripped before the next processing step. The most common techniques which have been used for photoresist stripping are the use of wet solvent developers such as sulfuric acid-hydrogen peroxide solution, and the technique of plasma ashing.
Further, during plasma etching processes, one or more layers of a film stack (e.g., layers of silicon, polysilicon, hafnium dioxide (HfO2), silicon dioxide (SiO2), metal materials, and the like) are typically exposed to etchants comprising at least one halogen-containing gas, such as hydrogen bromide (HBr), chlorine (Cl2), carbon tetrafluoride (CF4), and the like. Such processes cause a halogen-containing residue to build up on the surfaces of the etched features, etch masks, and elsewhere on the substrate. Abatement processes are used for removing volatile halogen-containing residues left from etching processes.
In the aforementioned processes, the gas distribution plate in the reaction chamber can become gradually contaminated. For instance, volatile reaction products and byproducts coated on the gas distribution plate result in obstruction of the gas flow openings of the gas distribution plate. This causes process drift and poor substrate to substrate repeatability. Additionally, volatile substances and byproducts (e.g., metal oxides) coating the gas distribution plate may promote oxygen recombination during ashing processes. As the level of contamination of the gas distribution plate increases, the ash rate correspondingly suffers degradation. This degradation can be up to 40% and is often the limiting factor for the number of substrates which can be processed between cleaning of the gas distribution plate. Thus, as the mean time between cleans (MTBC) diminishes, productivity suffers.
One method for extending the MTBC is to provide cleaning gas through the gas distribution plate during a specific cleaning operation after one or more substrates have been processed. However, performing cleaning operations consumes time in which substrates cannot be processed and costly aggressive gases which also attach chamber components. Thus, the use of cleaning gas limits productivity and process throughput.
Therefore, a need exists for reducing the contamination of gas distribution plates.